Chemical injection valves are core components in the subsea valve trees, but are also used for topside installations.
Chemical injection valves are used to inject a continuous flow of chemicals into a well to prevent clogging of the well and the flow line. Chemical injection valves are throttle valves that throttle the flow from a high pressure chemical supply line into an oil/gas flow line/well with less pressure. The chemical injection valve controls the magnitude of the chemical flow.
With all chemical injection valves and other small sized valves that have a restricted fluid passage there is a risk of debris getting caught in the fluid passage and clogging the fluid passage.
In accordance with prior art, an internal control system is arranged for flushing the valve if clogging is registered. Such control systems are vulnerable to clogging themselves because they usually involve small apertures that measure the flow by differential pressure. The control system that measures the flow operates either a piston or a motor that opens the throttling orifice if flushing is needed.
This prior art flushing system is relatively complex and the use of such a flushing system adds a vulnerability to the working of the valve arrangement, as the flushing of the clogged valves depend on the proper working of the valve arrangement. The use of the prior art flushing system causes a reduced flow rate due to the size of the measurement apparatus for monitoring the flow.
The invention proposes an alternative solution to the prior art control system by basing the inventive idea on a different set of principles to flush a clogged valve. As a consequence, the simplified inventive solution for flushing of the clogged valve assembly improves the reliability of the flow of fluid as it does not involve complex sensors, control systems and electric actuating means to flush the valve. A reliable flow of injection chemicals is a key factor for sustainable production from oil and gas wells and a sought after property for a chemical injection valve. Further, by employing the invention it is possible to obtain a larger flow range since the small measurement apertures used to monitor flow and clogging of the main orifice are not needed. The possibility of a larger flow range means that the variety of valve sizes can be reduced. This will simplify documentation and administration, give less room for delivery errors and make it more cost efficient to hold valves in store since one part number covers many needs.